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Massive oil loss at high speeds

3K views 16 replies 8 participants last post by  RedneckRam 
#1 ·
Howdy, so when I drive fast (70 mph), my engine will spit out about a gallon or so of oil with no warning. I'll just arrive at my destination missing a gallon of oil. (I check every time I drive it) The strange bit is that it doesn't lose even a drop during normal driving (45-55 mph), regardless of whether it's on the highway or around town. It also doesn't leave a drop on the ground when parked. However, when it does decide to dump it's oil, the drip pattern runs all the way to the back of the truck when parked. Does anyone have any ideas as to why it's doing this?
 
#4 ·
Ah shucks, that's a bummer :\ I guess it would make sense, I took it to a local diesel mechanic for a p-pump repair, and he said I was getting a decent amount of blow-by. I'm amazed it's gotten this bad in 5 months, however.
Is the only option to fix this a rebuild?
 
#5 ·
Do you get air out for the vents or only defrost?
 
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#8 ·
You thinking there’s a problem with his vacuum pump? I know those things are horrible about leaking oil. I wouldn’t go replacing the engine yet. Try taking the oil cap off and taping a rag over the hole so a bunch of dirt doesn’t fall down in there. Then go drive your truck 70+ mph for awhile. If it is excess blow by causing the problem it shouldn’t leak all that oil out with with the cap off.
 
#9 ·
I'd be willing to try that, but the only thing is the oil dump is pretty sporadic. It only happened three times in all in the last two months. I would definitely be willing to try that, though.
 
#11 ·
I had exactly the same problems a couple of years ago. The bottom line is that you are pressurizing the crankcase with combustion pressure the oil is blowing out your road draft tube. Remember that your crankcase vents to the atmosphere and there should be no pressure as in a gasser with an egr valve. My head had been rebuilt by a crappy machine shop and I was passing combustion pressure thru the valve train. You should be able to diagnose by pressurizing the cylinders one at a time and see which one leaks pressure. I had the same symptoms as I would not pass oil until i got some rps on the engine. By the way expect every gasket and seal to leak from now on until you pull the engine and replace.

sorry to deliver bad news
 
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#13 ·
I was wondering the other day about fitting a breather/ air filter over the fill tube. Remove the cap. Extra air. Probably not as good as valve covers, but an increase in flow????

I have one nearly the right size. If I remember I’ll try it tomorrow.

Unless someone posts a risk I’m not foreseeing.
 
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#14 ·
I did this a few years ago on my 95. That truck had almost perfect compression and still made a small mist of oil on the valve covers and head area. I measured the OD of the fill tube and then got on S&B site and found a small breather that clamped around it.
I used one of these https://www.sbfilters.com/shielded-clamp-on-crankcase-vent-filters
 
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#15 ·
And it worked? Did it plug up or need rinsing now and then?
 
#16 ·
Never plugged,there was no maintenance at all
 
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#17 ·
Thank you, everyone, for your help on this. I made a vent for the oil cap, and it seems to have solved the issue for the time being. God bless!
 

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